1. Field of the Invention
The present invention relates to image pickup apparatuses. More particularly, the invention relates to an image pickup apparatus suitable for performing imaging by changing the frame rate of an image signal after conducting signal processing, and more specifically, to an image pickup apparatus suitable for changing the setting of a signal processing operation in units of frame addition periods of a frame adder.
2. Description of the Related Art
Conventionally, in film production, to achieve special video effects, filming is performed while changing the speed of filming with a film camera, that is, changing the number of frames per second. For example, when filming is performed faster than normal speed and when playback operation is performed at normal speed, slow-motion playback images can be obtained. With this technique, high speed operation, such as a scene in which droplets are falling onto a water surface, can be easily and meticulously observed. Conversely, when filming is performed slower than normal speed and when playback operation is performed at normal speed, fast-motion playback images can be obtained. With this technique, a sense of speed in, for example, battle scenes or car chase scenes, can be increased so that the scenes become more realistic and have a greater impact.
In television program production, imaging, editing, and transmission of programs is being digitized. Due to the development of digital technologies, the image quality is becoming higher and the cost of devices for producing programs is becoming lower, and digitization of film production is also improving.
When performing imaging with an image pickup apparatus (video camera) in accordance with the digitization of film production, to obtain special video effects, not only image signals obtained by imaging with normal speed, but also image signals obtained by imaging at higher speeds or lower speeds, are recorded in a storage device, for example, a server. Then, image signals representing frame images required for obtaining special video effects are read out from the storage device, and image processing is performed on the read image signals, thereby producing special video effects.
To obtain special video effects, such as fast-motion playback images and slow-motion playback images, some image pickup apparatuses can change the frame rate during the imaging operation. Such an image pickup apparatus is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2000-125210. By using this image pickup apparatus, when imaging at a frame rate lower than a predetermined frame rate and when performing playback at the predetermined frame rate, fast-motion playback images can be easily obtained. In contrast, when imaging at a frame rate higher than a predetermined frame rate and when performing playback at the predetermined frame rate, slow-motion playback images can be easily obtained.
The frame rate can also be changed by performing frame addition processing. For example, when adding n frames of an image signal, the frame rate becomes 1/n.